Switching system comprising a source of liquified gas



Oct. 27, 1964 SWITCHING SYSTEM COMPRISING A SOURCE OF LIQUIFIED GASFiled April 27, 1961 o GAS F E iRlGERAToR t 1 1 10 11 3 2 l r\ K HEATzxfi em' EXCHANGER PRIOR ART P O.

6 T 7 COLD As 1 REFRIGERATOR I 1* 8 f 2 17 1 a 4 D D u 4 s V 21 525 3 22244 a '9 4 27 2s a z 929 27 INVENTOR United States Patent 3,154,394SWITCHING SYSTEM COMPRISING A SOURCE OF LEQUIFIED GAS Johannes van derSter, Emmasingel, Eindhoven, Netherlands, assignor to North AmericanPhilips Company,

lnc., New York, N.Y., a corporation of Delaware Filed Apr. 27, 1961,Ser. No. 106,022 Claims priority, application Netherlands May 6, 1960 3Claims. (CI. 62-40) The invention relates to a system comprising aplurality of vapor bubble or lift pumps for lifting a liquid, forexample, liquid gas. This liquid gas may be, for example, liquid air,nitrogen, methane, or the like.

A vapor bubble or lift pump is to be understood to mean a liquid uptakeimplement consisting of a short, wide duct or a vessel termed thedowntake duct which communicates with the lower end of a narrower uptakeduct, to which, at a place below the liquid level in the downtake ductheat can be supplied so that vapor bubbles are produced in the uptakeduct, which bubbles convey the liquid in the uptake duct in an upwarddirection in the manner of a gas introduced into the uptake duct of aso-called mammoth pump.

The invention provides a system in which such vapor bubble pumps areutilized in an advantageous and eificient manner.

In the system according to the invention vapor bubble or lift pumps withtheir heat supply devices, also termed heating devices, and with theiraccessories are used as switching elements. In this case they may serve,for example, to replace valves, of which the use, under certainconditions, for example, with very low temperatures and with liquid gastraversing the valves, may give rise to difiiculties in which the valvesare likely to be jammed.

The advantages of the system according to the invention are clearlymanifest in a system comprising a plurality of heat exchangers which areadapted to be switched over. This applies, for example, to a cold gasrefrigerator, which comprises, as is known, one or more walls (or heads)cooled during operation to an extent such that gas is condensed thereon.Gas, for example, air is conveyed towards this cold wall, preferably onits path to Wards the wall through a heat exchanger, constituents suchas carbon dioxide and water which form impurities of the condensate areseparated out of the gas.

Such heat exchangers are known from U.S. Patent No. 2,900,798 and fromU.S. Patent No. 2,899,381. In these patents the impurities are separatedout in the form of snow on cooled plates, along which is conveyed thegas to be purified.

An important further construction of such a heat exchanger is describedin U.S. Patent No. 2,999,364. In this case the impurities are separatedout in the form of snow on a partition which is pervious to the gas, forexample, a gauze partition, which is efficiently cooled. Such heatexchangers become clogged with snow after a given period of operation.The heat exchanger then has to be switched off in order to remove thesnow. In order to permit a continuous operation of the system, a secondheat exchanger, on which no snow has been formed is then switched on.

In one embodiment of the invention each heat exchanger in such a systemis connected, in order to change over the heat exchangers, to a vaporbubble pump and the heating devices for these pumps, are housed in aswitching system.

If the system comprises a cold gas refrigerator, the outlet duct forliquid gas of this cold gas refrigerator in a further embodiment of theinvention may be connected with the vapor bubble pumps while the heatexchangers are connected with the space around the cold 3,154,394Patented Oct. 27, 1964 head of the cold gas refrigerator and are adaptedto separate out impurities from the gas conveyed towards the cold head.

The heat exchangers may constitute units which communicate through aspace for the supply of gas vapor, with the space around the cold head.These units are arranged outside the cold head. The connecting ductsbetween the heat exchangers and the space around the cold head may thenbe formed by uptake ducts which are bent over in a downward directionfrom a place located above the head to the space around the head. Thisembodiment has an advantage which will be explained with reference tothe drawing.

The lower ends of the uptake pipes of the vapor lift or bubble pumps ina practical embodiment are arranged in a vessel to be filled with liquidgas so that this liquid blocks these lower ends. This vessel thenconstitutes the downtake pipes of the vapor bubble pumps. If a separatedowntake pipe is provided with a pump, this pipe may be arranged tosurround the uptake duct, so that the lower end of the latter is alsoblocked by liquid in the downtake duct.

The invention will be described more fully with reference to thediagrammatical drawing in which:

FIG. 1 shows a diagram of a known system comprising cocks or stopvalves,

FIG. 2 shows a diagram of one embodiment of a system according to theinvention, and

FIG. 3 is a fragmentary diagrammatic view of an alternate embodiment ofoutlet ducts.

Referring more particularly to the two diagrammatic drawings thereference numeral 1 designates a cold head and the space surrounding itin a cold gas refrigerator. In both diagrammatic drawings provision ismade of two heat exchangers 2 and 3, for example, of the kind describedin the aforesaid patents.

Gas to be purified can be supplied to each heat exchanger 2 and 3respectively at points 4 and 5. Subsequent to purification the gas canbe conveyed in these systems through the ducts 6 and 7 from the spacesin the heat exchangers 2 or 3 towards the cold head 1.

The gas to be purified may be also supplied to a heat exchanger 28 or 29at 4 or 5 and so conducted away subsequent to purification in the heatexchanger 28 or 29, through an outlet duct 8 or 9 as shown in FIG. 3.The ducts 6 and 7 then serve to conduct away gas or vapor suppliedthrough a dilferent duct, for example, the ducts 10 and 11 in FIG. 1, tothe heat exchangers 2 or 3 to cool the gas supplied to these heatexchangers through the ducts 4 or 5 As is shown in FIG. 7, liquid gascondensed on the cold head 1 is conducted away through the ducts 12 andby means of a three-way cock or valve 13 either to the duct 10 and theheat exchanger 2, or to the duct 11 and the heat exchanger 3.

The ducts 6 and 7 join at a three-way cock or valve 14, which is capableof supplying gas or vapor via the duct 15 to the chamber surrounding thecold head 1.

As is shown in FIG. 1, the cocks 13 and 14 are set first, for example,so that the heat exchanger 2 is operative. When this heat exchanger 2 isfilled with impurities from the gas supplied at 4 to a given extent, thecooks 13 and 14 are switched over, so that the heat exchanger 3 becomesoperative and the heat exchanger 2 can be purged of the collectedimpurities.

This known construction has the disadvantage that the cocks are likelyto be jammed. Moreover, the transition from the operation with one heatexchanger to the operation with the other heat exchanger is abrupt.These disadvantages are completely avoided in the system according tothe invention, of which an embodiment is shown in FIG. 2.

In this case, liquid gas obtained on the cold head 1 is conveyed throughthe duct 12 to a vessel 16. In this vessel the lower ends of uptakeducts 17 and 18 of vapor bubble pumps are arranged. The uptake duct 17communicates with the heat exchanger 2 and the uptake duct 18communicates with the heat exchanger 3.

The heating devices of the vapor bubble pumps are designated by 19 and20. They are formed in this case by electrically heated elements, ofwhich the current supply wires and the current outlet wires 21 and 22and 23 and 24 respectively are connected to terminals 25 and 26respectively of a switch 27.

The rising ducts 6 and 7, which conduct away gas or vapor from the heatexchangers, are bent over from a place P or Q respectively above thehead 1 downwards towards the head so that at P and Q heat barriers areformed. The cock 14 of FIG. 1 may then be completely dispensed with.

The cock 13 is replaced in FIG. 2 by the vapor bubble pumps, which canbe changed over by means of the switch 27. The switching device 27 maybe constructed so that it is adapted to co-operate first with the heatexchanger 2, so that liquid gas is conducted through the uptake duct 17,then with the two heat exchangers, so that the two vapor bubble pumpsare operative, and finally with the heat exchanger 3 and the vaporbubble pump 18.

The vessel 16 is to be proportioned so that a satisfactory change overis possible. The liquid in the vessel 16 constitutes at the same time asatisfactory insulation for the lower ends of the rising ducts 17 and 18of the vapor bubble pumps.

The system may comprise more than two heat exchangers, each of which isadapted to co-operate with vapor bubble pumps.

While I have shown and described the preferred embodiment of myinvention, it will be understood that the latter may be embodiedotherwise than as herein specifically illustrated or described and thatin the illustrated embodiment certain changes in the details ofconstruction and in the arrangement of parts may be made withoutdeparting from the underlying idea or principle of the invention withinthe scope of the appended claims.

What is claimed is:

1. A system for switching over heat exchangers associated with a coldsource comprising a plurality of heat exchangers adapted to be switchedover, means for feeding gas to said heat exchangers and said cold sourceand condensing the output therefrom to form liquified gas, a vesselhaving its bottom located at a level below the bottoms of said heatexchangers, a conduit connecting said cold source to said vessel wherebysaid liquified gas is conducted thereto and stored therein, a pluralityof vapor lift pumps having the lower ends thereof submerged in theliquified gas in said vessel and upper ends in communication with saidheat exchangers which are adapted to transport said liquified gas in anupward direction to said heat exchangers; heating devices for each vaporlift pump, a source of power, and current supply wires provided with aswitch for electrically connecting said source of power to selectedcurrent supply wires whereby said vapor lift pumps are electricallyactuated and function as switching elements for said heat exchangers.

2. A system for switching over heat exchangers associated with a coldsource as claimed in claim 1, wherein said means for feeding gas to saidcold source from said heat exchangers are U-shaped rising ducts whichare so constructed as to prevent cold from the cold source returningtherethrough to said heat exchangers.

3. A system for switching over heat exchangers associated with a coldsource as claimed in claim 1, wherein the latter is a cold gasrefrigerator.

References Cited in the file of this patent UNITED STATES PATENTS572,449 Rich Dec. 1, 1896 2,002,941 Frankl May 28, 1935 2,008,334 FranklJune 22, 1937 2,637,531 Davidson May 5, 1953 2,651,508 Bready Sept. 8,1953 2,677,252 Rice et a1. May 4, 1954 2,749,714 Hunter June 12, 19562,853,953 Hallman Sept. 30, 1958 2,958,203 Trepp Nov. 1, 1960 2,959,926Haringhuizen Nov. 15, 1960 2,963,874 Means Dec. 13, 1960 2,964,916Keeping Dec. 20, 1960 FOREIGN PATENTS 776,186 Great Britain June 5, 1957

1. A SYSTEM FOR SWITCHING OVER HEAT EXCHANGERS ASSOCIATED WITH A COLDSOURCE COMPRISING A PLURALITY OF HEAT EXCHANGERS ADAPTED TO BE SWITCHEDOVER, MEANS FOR FEEDING GAS TO SAID HEAT EXCHANGERS AND SAID COLD SOURCEAND CONDENSING THE OUTPUT THEREFROM TO FORM LIQUIFIED GAS, A VESSELHAVING ITS BOTTOM LOCATED AT A LEVEL BELOW THE BOTTOMS OF SAID HEATEXCHANGERS, A CONDUIT CONNECTING SAID COLD SOURCE TO SAID VESSEL WHEREBYSAID LIQUIFIED GAS IS CONDUCTED THERETO AND STORED THEREIN, A PLURALITYOF VAPOR LIFT PUMPS HAVING THE LOWER ENDS THEREOF SUBMERGED IN THELIQUIFIED GAS IN SAID VESSEL AND UPPER ENDS IN COMMUNICATION WITH SAIDHEAT EXCHANGERS WHICH ARE ADAPTED TO TRANSPORT SAID LIQUIFIED GAS IN ANUPWARD DIRECTION TO SAID HEAT EXCHANGERS; HEATING DEVICES FOR EACH VAPORLIFT PUMP, A SOURCE OF POWER, AND CURRENT SUPPLY WIRES PROVIDED WITH ASWITCH FOR ELECTRICALLY CONNECTING SAID SOURCE OF POWER TO SELECTEDCURRENT SUPPLY WIRES WHEREBY SAID VAPOR LIFT PUMPS ARE ELECTRICALLYACTUATED AND FUNCTION AS SWITCHING ELEMENTS FOR SAID HEAT EXCHANGERS.